1. Field of the Invention
The invention is relative to a cylinder sieve machine, also known as a cylinder machine, cylinder mold machine, or board machine, in particular to a tumbling sieve machine. The invention concerns the sieve insert of such a machine.
2. Description of the Related Art
Such machines are known from a great number of publications. The machine comprises the following components: A level sieve that is generally round, consists of a fabric or woven cloth that comprises meshes. The machine also comprises a rebound bottom, also known as an impact bottom or baffle bottom. This rebound bottom is also level and circular and consists of a perforated sheet. The rebound bottom is arranged a certain interval from and parallel to the sieve. The sieve and the rebound bottom form two separate units.
Rebound bodies are arranged in an intermediate area between the sieve and the rebound bottom. They usually consist of rubber balls.
When the machine is in operation the material to be sieved is charged from above onto the sieve. The rebound bodies execute a knocking and wiping movement due to the motion of the machine and strike from below against the sieve. Particles of the material to be sieved that are stuck in the sieve meshes are loosened thereby so that the sieve is subjected to a constant cleaning.
The cleaning of the sieve is decisive for the degree of effectiveness of the entire sieving process. Numerous attempts have been made to improve the cleaning; nevertheless, improvement is still required.
The invention is based on the problem of designing a sieve insert for a machine of the specified type in such a manner that the cleaning is improved in comparison to known sieve inserts.
In the case of the known sieve inserts a chaotic displacement, creeping, or migration of the rebound bodies takes place in the intermediate area between the sieve and the rebound bottom. The rebound bodies execute not only the cited up and down movement but also other partial movements, e.g., creeping or migratory movements around the machine axis or movements transversely to it. The inventors recognized that it is favorable for the cleaning process to suppress these creeping movements. The optimum is a movement of the rebound bodies that is substantially up and down with relatively slight creepings in other directions.
The solution consists according to the invention in that the sieve is subdivided into sieve segments and that the sieve frame supports the sieve segments along their contours or edges. This achieves the goal that the support brings in that the rebound bodies remain in the area of that sieve segment in which they are located.
The subdivision of the sieve into a plurality of sieve segments has yet another advantage; if a sieve segment is damaged during the course of operation, only this one sieve need be replaced instead of the entire sieve, as previously accomplished. This is on the one hand more cost-effective and on the other hand it requires a lesser assembly expense. The storage of the sieve segments is less expensive, so that less capital is tied up. In addition, the manipulation becomes much easier, which is to be explained further below.
A very important advantage is constituted by the fact that when the entire sieve surface consists of a single sieve a certain sagging of the sieve will develop, at least in the passage of time. However, each sag represents a non-uniform wear of the sieve, viewed over the sieve surface. If, instead of the above, the sieve surface is subdivided into a plurality of sieve segments, accordingly smaller surfaces are involved. The sag is sharply reduced, if even still present at all, and the wear is largely uniform over the entire surface of the sieve segment.
The basic cited concept of the invention can be further developed as follows; instead of subdividing only the sieve and the frame, complete, autarkic sieve segments can be created, each of which comprises a sieve segment, a partial rebound bottom as well as a partial sieve frame. Moreover, such a construction has the advantage of being easier to manipulate and maintain.
It is also possible to select sieve segments that differ as regards their sieve qualities. Of course, each sieve segment must be associated with its own outlet for the material that passed through it.